Wheelchairs are commonly used by people with ambulatory problems. A common issue with wheelchairs is that they do not easily roll or otherwise progress up and down step-like or elevated structures, such as sidewalk curbs; and if they do, it is typically via a complex mechanism and/or a mechanism that causes the user to be tilted, which can be uncomfortable or even dangerous to the user, as well as expensive.
The following publications are believed to represent the current state of the art: U.S. Pat. No. 6,554,086 (Goertzen et al., Apr. 29, 2003); U.S. Pat. No. 8,292,010 (Puskar-Pasewicz, et al., Oct. 23, 2012); U.S. Pat. No. 7,316,282 (Mulhern et al., Jan. 8, 2008); U.S. Pat. No. 7,360,792 (Turturiello et al., Apr. 22, 2008) US 2010/096194 (Starcevic, Apr. 22, 2010); and WO 1998/046184 (Schaffner et al., Oct. 22, 1998) all of which are incorporated herein by reference in their entirety.